This invention relates generally to a hydraulic system and, more particularly, to providing a down force on an actuator connected to a work implement.
Planter row units are typically supported from a transverse frame by vertically spaced parallel arms, which permit each row unit to vertically pivot independently to follow ground contour. Down force on the furrow openers mounted on parallel arms is normally assisted with springs, and adjustments to the down force is made by adjusting the pressure of operating fluid supplied to a hydraulic adjustment cylinder. The adjustment cylinder applies force to a rock shaft or other pivotal arrangement that is connected to the row units. A hydraulic control circuit allows the operator to make adjustments to the down force as the soil conditions change during operation.
One such implement and control circuit is disclosed in U.S. Pat. 5,163,518 issued on Nov. 17, 1992 to Deere and Company. The control circuit disclosed in this patent uses an adjustable pressure control device positioned in series with the flow control valve. The operator sets the pressure control device to a specific operating pressure so that when the adjustment cylinder is actuated the desired down pressure is applied to the row units. Since the flow control valve is left in an operating position for extended periods of time excessive heat is introduced into the hydraulic system. This consumes large amounts of power, reducing the available power to other tractor systems.
The present invention is directed to overcoming one or more of the problems as set forth above.
In one aspect of the present invention a hydraulic system for a work implement that is towed by a work machine is provided. The hydraulic system includes a source of pressurized fluid. A first control valve is connected to the source of pressurized fluid. A second control valve is also connected to the source of pressurized fluid. A fluid motor is connected to the first control valve by a supply conduit and a return conduit. An actuator having a down force end is connected to the second control valve by a conduit and a lift end is connected to the second control valve by a conduit. A pressure responsive valve is disposed between the supply conduit and the down force end of the actuator and movable between a first position communicating the supply conduit with the down force end of the actuator and a second position blocking supply conduit from the down force end of the actuator.
In another aspect of the current invention a method for controlling operation of a work implement that has a seed/fertilizer supply system and a plurality of individual row units. The method includes the steps of actuating a fluid motor of a first control circuit for transporting seed/fertilizer from the seed/fertilizer supply system to the plurality of row units. Operating fluid is then supplied to a down force end of an actuator of a second control circuit for lowering the plurality of individual row units. A predetermined pressure is applied on the down force end of the actuator to apply down force on the plurality of individual row units. The plurality of rows units are then placed in a float mode. And last, communicating operating fluid from the first control circuit to the down force end of the actuator to maintain down force on the plurality of row units.